Gas developing apparatus



United States Patent [72] Inventor Joseph l-lruby Deerfield, Illinois 2|AppLNo. 577,402 [22] Filed Sept. 6,1966 [45] Patented Aug.l8,1970 [73]Assignee Addressograph Multigraph Corporation Mount Prospect, Illinois aCorp. of Delaware [54] GAS DEVELOPING APPARATUS 6 Claims, 3 DrawingFigs.

s21u.s.c| 95/94, 95/89 151] Int.Cl G03d3/l2 003(13/00 [50] Field ofSearch 95/94Gas.M, 89Gas,M; 34/46 134, 155

[56] References Cited UNITED STATES PATENTS 2,208,106 7/1940 Schade eta1 95/89UX 2.299,045 10/1942 Trump 95/89 2,431,041 11/1947 Hassler 95/89FORElGN PATENTS 85,034 1/1930 Japan. 615,931 6/1947 Great Britain.650.464 2/1951 Great Britain. 842,691 7/1960 Great Britain. 987,8903/1965 Great Britain.

Primary Examiner- Norton Ansher Assistant Examiner- Charles E. SmithAnorney- 501 L. Goldstein ABSTRACT: A developer unit comprising adeveloping chamber, gas generator and a blower. The developing chamberis provided with flexible entry and exit sealing members and atransporting unit within the chamber to transport a copy sheettherethrough between the entry and exit members. The gas generator isconnected to the chamber by independent inlet and outlet conduits. Theblower is used to circulate a predetermined volume of gas from thegenerator within the chamber and back to the generator.

Patented Aug. 18, 1970 3,524,397

Jul/enforame v14 Eur Patented Aug. 18, 1970 Sheet Z of2 GAS DEVELOPINGAPPARATUS This invention relates to gas type developing apparatus fordeveloping light-sensitive sheet material and, more particularly, to anarrangement for supplying a gas enriched atmosphere generated at alocation remote from the developing site for use when copy sheets arebeing developed and stopping the supply during idle periods.

In the photocopying art, a two-component diazotype lightsensitivematerial, which has first been exposed to a light image, is developed toproduce thereon an azo-dye image by bringing the copy sheet into contactwith a humidified atmosphere of ammonia vapor. The ammonia vapor isproduced by heating an ammonium hydroxide solution or by the use ofanhydrous ammonia gas. The construction of known copying equipment fordeveloping copy sheets of this type involves the use ofa gas chamber inwhich the ammonia vapor is generated directly from a tank containingammonium hydroxide solution or the ammonia vapor is piped in from tanksof anhydrous ammonia which is admixed with water vapor generated withinthe gas chamber. Generally, the equipment is maintained in a fulloperating condition during the working day once it has been started up,which means that the ammonia gas producing instrumentalities are incontinuous operation while the machine IS on.

The gas producing instrumentalities usually call for circulatory pumpingequipment which continually supplies fresh ammonium hydroxide and/oranhydrous gas into the chamber maintaining the chamber in a state ofreadiness to receive the copy sheets.

Photocopying machines relying on the gas developing process as a meansfor producing copies, are desirable because the process is dry,obviating the need for bringing liquid materials into direct contactwith the copy sheet for development; it produces azo-dye images of highdensity; and is capable of developing copies at a rapid rate. lnherentin the use of such equipment is the requirement to place it underexhaust to the outside atmosphere in order to remove the noxious ammoniavapor from the working environment.

Another problem experienced with these developing devices is thecondensation of the water vapor on the humidified developing chamberresulting in the deposition of condensate on the rollers or belts whichconvey the copy sheet through the chamber so that when the copy sheetcomes in contact with the wet surfaces, it mars the image. Accordingly,shutting down the developing chamber at the end of the copy makingoperation requires controlling the environment therein, such as the useof heaters in order to prevent the con- 'densate from forming.

It will be appreciated from the foregoing discussion that due to thecomplexity of the heretofore known gas developing equipment, itsadvantages were not available in small desk-top copiers for office usewhere the copying demand is, at best, occasional or only intermittent.The requirements for complex feed systems and heating systems related tothe developing chamber made such equipment impractical and too expensivefor the low-cost machine copying field.

Attempts have been made to produce a machine which has a simplified gaschamber construction in which the ammonium hydroxide is flushed throughan open channel in the developing chamber in order to enrich theatmosphere with ammonia and immediately drained out. While this providesa simplified arrangement, the concentration of gas in the chamber willvary greatly leaving it to the judgment of the operator to determinewhen the chamber is again to be exposed to ammonium hydroxide solution.

Now, in accordance with the present invention, a simplified. inexpensivegaseous developing apparatus designed for the intermittent copydemandsoccasioned in office-type installations is provided which ostensiblyeliminates the need for auxiliary exhaust equipment, is simple tooperate, which produces high quality copies consistently.

A primary object of the present invention is to provide a simplified,low-cost, gaseous developing apparatus capable of intermittent use whichemploys a humidified-ammonia enriched atmosphere in the developingchamber.

Another object is to provide an improved gas developing apparatus inwhich the ammonia enriched and humidified developing atmosphere iscirculated through the developing chamber having been generated at alocation remote from the chamber and which apparatus does not requireexhaust to the outside atmosphere.

lt is another object to provide a developing apparatus in which the copysheet passes through an ammonia enriched atmosphere which is forcecirculated through the chamber.

It is another object of this invention to provide an improved developingmethod for developing copy material by passing it through an enclosedchamber filled with an ammoniacal vapor enriched atmosphere, saidatmosphere being generated and maintained at a predetermined level ofenrichment at a station remote from the developing chamber.

In accordance with these and many other objects an embodiment of thisinvention comprises a gas developing chamber formed by enclosing a copysheet conveying assembly with an outer shell. The sheet conveyingassembly for carrying the exposed diazo copy sheet through the chambercomprises a large drum rotatably mounted within the enclosure. A feed-instation and an exit station are provided by rollers placed in drivingengagement with the periphery of the copy drum, one located at eachstation. The distance around the periphery of the drum between thesestations determines the minimum length of copy that can be safelyhandled by the copy carrying assembly. 7

The gas developing chamber that is formed in the space around the copyconveying assembly is closed due to the atmosphere in its immediatevicinity by sealing means located at the respective stations. Theopening between the shell and the respective rollers is effected byflexible flap means which contacts the feed-in roller along its entireextent and at the exit station, closure is effected by a similar flapurged against the drum so as to have the nipping portion between theexit roller and the drum contained within the enclosure. The flap at theexit portion is sufficiently flexible so that the sheet of paper beingadvanced by the exit roller and the drum can lift the flap in order tomove out of the enclosure. The aforedescribed.

sealing technique is intended to close off the atmosphere inside thechamber so that it is prevented from mixing with the. general roomatmosphere in which the apparatus is located.

A series of guide members are disposed around the periphery of the drumsurface guiding the copy sheet in apath around the periphery of the drumleading to the nip between the exit roller and the drum. In this mannerthe path of the copy sheet is controlled so as to assure the lead edgeentering the nip between the exit roller and the drum while the tail ofthe copy sheet is still under the influence ofthe roller at theentryway.

The gas developing atmosphere that is necessary to create theenvironment in which an azo-dye image can be formed is produced in a gasgenerator remote from the gas developing chamber proper. The gasgenerator can comprise any means for producing an ammoniaenriched-humidified atmosphere captured in a closed container. In theinstant invention, a-large closed container is partially filled with aconcentrated ammonium hydroxide solution maintained in a temperaturerange from room temperature to about F., preferably slightly above roomtemperature. The atmosphere above the liquid will contain an amount ofammonia and water vapor equal to the vapor pressure of the ammonia andwater vapor'at the particular temperature. The portion of the gasgenerator above the liquid level is placed in communication with the gaschamber through suitable air ducts leading into and out of the gaschamber and having an exhaust blower in the exit duct from the chamberto the gas generator. In this manner, an ammonia vaporenriched-humidified atmosphere is applied to the chamber on demand andthe supply stops when the blower stops. Except for the residualatmosphere in the chamber, the supply of ammonia to the chamber stopswhen the demand for copying stops. The force circulation keeps theconcentration of ammonia in the system at a level that is in equilibriumwith the ammonia content of the liquid in the gas generator. As ammoniais depleted from the atmosphere it is continually replenished as it isrecirculated through the gas generator.

It has been found that in the technique embodied in this invention theconcentration of ammonia in the atmosphere produced in the gas generatorand the humidity of the atmosphere are sufficiently high to insureproper development of the copy material processed through the developerunit. It has been found that starting with a 26 Baum ammonium hydroxidesolution maintained at 70-75" F. the ammonia that can be produced in adeveloping chamber of approximately 0.3 cubic feet is sufficientlyconcentrated to rapidly develop a dense azo-dye image. The concentrationofammonia and relative humidity can be maintained as the Baum of thesolution in the gas generator decreases due to the depletion of ammoniaused up in developing the azo copies, by increasing the temperature ofthe solution. For example, at 24-25 Baum, the abovedescribed ammoniaconcentration and relative humidity can be maintained by heating thesolution in the gas generator to a temperature of 80-90 F. At a 22-23Baum value the effectiveness of the solution can be maintained byincreasing its temperature to 90-I00 F. This process of heating thecharge solution may be kept up until the solution reaches a Baum valueof -21 which is deemed a practical limit beyond which the evolution ofammonia requires greater heat input. However, if desired, heating thesolution may be continued at lower Baum levels.

Other materials may be used as the source of ammonia vapor other thanammonium hydroxide such as (NH CO;, contained in an inert fluid such assilicone oil or paraffin oil. The ammonia carbonate is placed in the gasgenerator 24, covered with the inert liquid and when heated to suitabletemperature, ammonia gas bubbles through the inert liquid layer. Theliquid seals the (NH CO during periods when no copies are being made. i

At the relative humidity levels described above, the problem ofcondensate accumulating in the developing chamber is obviated.

Many other objects and advantages ofthe present invention will becomeapparent from considering the following detailed descriptions inconjunction with the drawings in which:

FIGURE l is a perspective view ofthe developing apparatus of thisinvention with portions of the outer shell broken away to show the sheetconveying assembly;

FIGURE 2 is a sectional view taken along line 2-2 of FIG. 1 showing thegas generator connected to the gas chamber;

FIGURE 3 cross sections the developer apparatus taken along line 3-3 ofFIG. 1.

Referring to FIGURES l and 2, there is shown an embodiment of the gasdeveloping apparatus of this invention, generally indicated as 10,having an inlet 12 for receiving a copy sheet S and a copy deliverystation I4 for receiving the developed copy sheet. Enclosing a rotatablymounted drum 16 there is provided a rectangularly shaped box or shell 18including side walls 20 which serve to support the drum mounted on ashaft 21 which is received in suitable bearings through the side walls.Enclosure l8 surrounding the drum provides a gas developing chamber [8Awhich is in communication with a gas generating assembly 22 (FIG. 2comprising a gas generator 24 equipped with a feed and exhaust conduit26 and 28, respectively, and the motor operated blower 30 to forcecirculate the active gaseous medium passing through the conduit system.

The transport ofthe copy sheets, as is best shown in FIG. 3, fed in fromthe inlet 12 to the copy delivery station 14, is accomplished by therollers 34 and 36 mounted on shafts 38 and 40, respectively, and beingrotatably mounted within the chamber 18A between the side walls 20 andin rolling contact with the drum 16. The rollers 34 and 36 are spacedfrom each other around the periphery of the drum a predetermineddistance; it is this distance which determines the shortest length ofpaper which the developer unit will be capable of handling. The drum l6and roller 36 are driven through a gear train comprising gears 44, 46and 48 axially mounted on the extensions of the shafts 38, 21, 40,respectively. The shaft 38 is driven by a motor 50 through a couplingconnection 52 thereby driving the copy transport assembly.

The inlet 12 is formed of a pair of converging, curved guideplates 56and 58 so as to form a guideway that changes direction of the copy sheetapproximately 180 after it enters the inlet 12, directing it to the nipbetween the drum l6 and the feed roller 38. Superimposed around the drumis a paper guide structure 60 comprising a series of arcuately shapedsupports 64 at spaced intervals along the length of the drum mounted onthe tie rods 65 disposed between the walls 20 and extendingcircumferentially around the drum covering the distance between therollers 34 and 36. The copy sheet S may be more positively urged toconform to the surface of the drum by the use of projecting fingers 66which are made of a resilient plastic or light metal construction. Withthe aid of the paper guide structure 60 the copy sheet is positivelydirected through the chamber along a predetermined path to the nipformed between the roller 36 and the drum 16 where it is gripped anddriven to the copy delivery station 14.

In order to complete the closure of the gas chamber 18A from theatmosphere at the point where the shell 18 meets the rollers 34 and 36,flexible flap extensions 67 and 69 are provided which form seals betweenthe roller 36 and the shell 18 and between the shell 18 and the drum inthe case of flap 69. The flaps may be formed of a thin flexible sheetmetal or plastic material. Sealing flaps made of a fluorocarbonpolyester material sold under the trade name Teflon have been verysuccessful since they are sufficiently resilient to engage theparticular rotating surface, and have a low coefflcient of frictionwhich permits the copy paper to escape this resilient force ofthe flap.

Referring to FIG. 2 the gas generator 24 may comprise any closed vesselsuch as, for example, a large polyethylene bottle ranging in capacityfrom 3 to 10 liters into which is charged the source of the ammoniavapor 70. In the preferred embodiment :1 26 Baum solution of ammoniumhydroxide is used. The vessel 24 is filled to about one-half totwo-thirds its capacity leaving an air space 72 above the liquid levelinto which is accumulated the ammonia and water vapors.

The gas generator is charged with a 26 Baum ammonium hydroxide solution(29.471 molal concentration of ammonia) and permitted to come to roomtemperature. Upon the startup of the developer apparatus, the blower 30is energized which begins to circulate the air from the gas chamber 18Athrough the air space 72 where it becomes enriched with a sufficientconcentration of ammonia vapor and water vapor to develop a diazo copypassing through the chamber at the rate of6 to 8 feet per minute.

In the instant invention the gas chamber may range from 0.25 cubic feetto 0.5 cubic feet, preferably about 0.3 cubic feet, is maintained with asufficient concentration of ammonia-water vapor from a 3 to 5 litersupply of 26 Baum ammonium hydroxide maintained at 55 to 75 F. Afterseveral hours of operation, the Baum value of the ammonium hydroxidedrops due to the depletion of ammonia from the system and, hence, thevapor pressure correspondingly decreases. Obviously, the depletion ofammonia occurs due to the usage of ammonia in carrying out thedevelopment of copy sheets and also from the small amounts of leakagefrom the system.

To correct for the decrease in ammonia concentration resulting from thelower vapor pressure, the solution in the gas generator is heated bymeans of a heating coil 74 or other suitable means to a temperature ofto F. thereby increasing the vapor pressure. The use of heat in thismanner may be continued until the Baum value drops to about 20 which isthe practical level at which the liquid in the generator emits ammonia.It can be heated until still lower Baum levels, but the efficiency dropsoff. It has been found that from an initial charge of3.8 liters of 26Baum the apparatus will process between 32,000 square feet to 36,000square feet of diazo copy processed through a gas chamber having avolume of 0.3 cubic feet and passing through at the rate of7 feet perminute.

The apparatus is placed in operation at the time it is required toreproduce one or more diazo copies by starting the drive motor 50 whichsimultaneously energizes the blower 30 which pulls the atmosphere fromthe chamber 18A and exhausts it into the air space 72 of the gasgenerator through the conduit 28. The force flow of air into the space72 causes it to absorb the ammonia-water vapors and return in an ammoniaenriched condition through the return conduit 26.

As soon as the blower 30 is turned on the operator may begin feeding thecopy sheets into the inlet 12 to be developed. At the conclusion of thedeveloping cycle the operator turns off the machine by turning off thedrive motor 50, as soon as all copies clear the apparatus, which turnsoff the blower and stops the flow of ammonia to the chamber 18A. In itsinoperative condition only the residual ammoniacal atmosphere remains inthe chamber [8A which is contained by the sealing flaps 67 and 69.

The return conduit 26 may optionally be equipped with a conventionalshutoff damper 76 that can be manually operated or electricallycontrolled such as by a solenoid 78 concurrent with the energization 0rdeenergization of drive motor 50 in the same manner as the blower. Thedamper 76 closes the chamber 18A from receiving any wafts of ammoniathrough the conduit 26 during periods of inoperation. The blower in theconduit 28 closes off the access from the gas generator to the chamber.

lclaim:

l. A gas developer unit adapted for the intermittent processingoftwo-component diazotype copy sheets, the combination comprising:

a gas developing chamber closed from the general atmosphere providing apredetermined gas processing volume,

separate entryway means and exit means for processing said copy sheetthrough the chamber,

sealing means provided at both said entryway means and said exit meansfor permitting ingress and egress of a copy sheet to said chamber whilemaintaining said chamber substantially sealed from the generalatmosphere,

copy transport means within said chamber for transporting said copysheet through said chamber between said entryway means and said exitmeans along a predetermined path therebetween, for exposing said copysheet to said gaseous atmosphere therein,

independent gas generating means located outside said chamber forgenerating a supply of ammonia vapor,

conduit means placing said gas generating means in twoway communicationwith said gas chamber, and

control means including damper means in said conduit means forcontrolling the flow between said generating means and said chamber andblower means coupled to said conduit means, said damper and blower meansbeing operable between a copying and off condition for controlling themovement of ammonia vapor from said generating means into said chamberand from said chamber back to said generating means, said damper andblower means both being operated in said copying condition whereby saidpredetermined volume is circulated through said generating means duringthe copying condition and during the off condition forced circulationceases.

2. The developer unit as defined in Claim 1 wherein said generatorincludes a reservoir containing an aqueous ammonia liquid for generatingsaid gaseous agent.

3. The developing unit as defined in Claim 1 wherein said gas generatingmeans is charged with an ammonia gas producing material to a level lessthan its capacity to provide an air space thereabove whereby saidammonia gas is permitted to accumulate in said air space.

4. The developing unit as defined in Claim 3 wherein said gas producingmaterial is a concentrated aqueous ammonium hydroxide solution rangingfrom 20 Baum to 26 Baum.

5. The developing unit as defined in Claim 1 wherein said gas generatingmeans includes heater means for heating the ammonia producing agent.

6. A developer unit for developing a diazotype copy sheet comprising:

A developing chamber sealed from the general atmosphere,

separate entryway and exit means provided in said chamber for processinga copy sheet through said chamber,

sealing means provided at both said entryway means and said exit meansfor permitting ingress and egress of a copy sheet to said chamber whilemaintaining said chamber substantially sealed from the generalatmosphere,

copy transport means within said chamber for moving said copy sheetthrough said chamber between said entryway means and said exit means,for exposing said copy sheet to said atmosphere therein, said copytransport means including a rotatable drum and paper guide meanscomprising a resilient conforming guide member disposed adjacent thesurface of said rotatable drum for urging a copy sheet to conform to thesurface of the drum as the copy sheet is moved thereby through saidchamber,

gas generating means located outside of said gas developing chamber forgenerating a diazo-developing gaseous agent, and

means connecting said gas generating means and said gas chamber,comprising a gas supply conduit and gas return conduit for respectivelyconducting developing gas from said generating means to said chamber andfrom said chamber to said generating means, and circulating meansassociated with said conduit means for positively circulating apredetermined volume of developing gas from said generating meansthrough said conduit means and said developing chamber.

